1. Field
The present disclosure relates generally to metamaterials. More particularly, the present disclosure relates to a method and apparatus for adjusting a resonance of a metamaterial structure using a tunable element associated with the metamaterial structure.
2. Background
A metamaterial may be an artificial composite material engineered to have properties that may not be currently found in nature. A metamaterial structure may be an assembly of multiple individual metamaterial cells that are formed from conventional materials. These conventional materials may include, but are not limited to, metals, metal alloys, plastic materials, and other types of materials.
The refractive index for a metamaterial cell is determined by the electric permittivity and magnetic permeability of the metamaterial cell. The refractive index determines how an electromagnetic wave propagating through the metamaterial cell is bent, or refracted. A negative index metamaterial (NIM) is a metamaterial that provides a negative index of refraction over a particular frequency range that is typically determined by the resonance of the metamaterial. This frequency range is typically a band of frequencies centered at or near a resonant frequency of the metamaterial. The frequency range over which the negative index of refraction is provided by a metamaterial structure may be dependent on various factors including the orientation, size, shape, and pattern of arrangement of the metamaterial cells that form the metamaterial structure.
A metamaterial structure may take the form of a two-dimensional or three-dimensional periodic structure of self-resonant metamaterial cells that are each typically self-resonant within the same frequency range, which may be a limited or narrow frequency range. The aggregate effect provided by this type of metamaterial structure may be used to focus electromagnetic energy in a manner similar to an optical lens.
While the negative index of refraction effects of metamaterial structures provide a powerful means of directing electromagnetic energy, these metamaterial structures have a limited operational frequency range. Increasing the range of frequencies over which a negative index of refraction may be provided by a particular metamaterial structure may be useful in certain applications. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.